Four years after its launch, Swisscube, the small satellite developed by EPFL's Space Center, is still in operation. Some of the technological choices made and considered audacious at the time have yielded valuable lessons ...

(Phys.org) —Research by Murdoch University, James Cook University and the University of Waterloo in Canada has revealed flaws in the way that the widely-used Ångström-Prescott equation links solar radiation to sunshine ...

A surprise flurry of meteors or "shooting stars" caught the eye of several casual observers in Western Europe on the night of 9–10 September. The meteors were apparently quite fast, with some bright enough to qualify as ...

(Phys.org) —When a major wildfire destroys a large forested area in the seasonal snow zone, snow tends to accumulate at a greater level in the burned area than in adjacent forests. But a new study found that the snowpack ...

Is your cable television on the fritz? One explanation, scientists suspect, may be the weather—the weather in space, that is. MIT researchers are investigating the effects of space weather—such as solar flares, geomagnetic ...

The Sun-grazing asteroid, Phaethon, has betrayed its true nature by showing a comet-like tail of dust particles blown backwards by radiation pressure from the Sun. Unlike a comet, however, Phaethon's tail doesn't arise through ...

A team of scientists from Southwest Research Institute (SwRI) has demonstrated that frozen water in the form of snow or frost can melt to form debris flows on sunward-facing slopes of sand dunes in the Alaskan arctic at air ...

Sunlight

Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. Near the poles in summer, the days are longer and the nights are shorter or non-existent. In the winter at the poles the nights are longer and for some periods of time, sunlight may not occur at all. When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat. Radiant heat directly produced by the radiation of the sun is different from the increase in atmospheric temperature due to the radiative heating of the atmosphere by the sun's radiation. Sunlight may be recorded using a sunshine recorder, pyranometer or pyrheliometer. Sunlight takes about 8.3 minutes to reach the Earth. The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 watts per square metre.

Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, which includes infrared, visible, and ultra-violet light. Bright sunlight provides luminance of approximately 100,000 candela per square meter at the Earth's surface.

Sunlight is a key factor in photosynthesis, a process crucially important for life on Earth.